The purpose of this program is to examine systematically some of the conditions under which recovery of function might appear after damage to the somatosensory cortex and thalamus. The serial lesion effect (the observation that brain lesions made slowly over time may be less detrimental to the functioning of the organism than equivalent damage produced in one sitting) is the subject of some of these projects. In particular, the interaction of the interoperative interval and the postoperative recovery period will be examined as they relate to tactile performance after sequentially produced lesions of the somatic cortex in rats. Other projects dealing with serial lesions are designed to see whether a serial lesion effect can be obtained with damage in a subcortical sensory area (ventrobasal thalamus), and to test the hypothesis that the substrates underlying recovery might differ after one-stage and serial surgery. A second class of experiments will concern itself with lesions of the somatosensory cortex in infant rats and cats. These investigations will ask whether age is always a significant factor in recovery from these lesions. The third type of experiment will look at the contribution of the postoperative recovery period in behavioral research. Some of these studies will look at whether there might be some sort of time-dependency recovery after lesions of S-1 or S-2 in rats (no such recovery has been demonstrated in the past when both areas were bilaterally ablated together). In addition to these studies, one electrophysiological investigation on the directional sensitivity of rat's vibrissae (cortical unit recording) will be conducted. The purpose of this work will in part be to try to define a mini-system for even more refined research on recovery of function. The present program should contribute significantly to an understanding of the conditions necessary for recovery of function, especially in the context of the earlier studies on which they are based. Projects from this laboratory have in the past shown that very different syndromes can emerge from seemingly identical lesions. Some of the variables underlying this observation will now be delineated.